Field of the Invention
The invention relates to a current mirror.
Whenever neither of the two terminals of a consumer to be operated with an impressed current can be allowed to be connected to a fixed potential, so-called "floating current sources" are employed. They are known, for instance, from the book entitled "Halbleiter-Schaltungstechnik" [Semiconductor Circuitry] by U. Tietze and C. Schenk, 8th Edition, 1986, pp. 363-364, and include two grounded current sources that provide opposite currents of equal magnitude and supply the consumer through the respectively other current source. It is essential that both current sources produce currents that are as exactly equal in magnitude as possible. However, that demand is all the harder to meet if the current sources are supposed to be controllable in accordance with a common input variable. That is the case in a current mirror, for instance, which is intended to generate a potential-free output current that is proportional to an input current which does have a potential.